JP4406111B2 - Polishing liquid composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing liquid composition for polishing a surface to be polished having an insulating layer and a metal layer. More particularly, the present invention relates to a polishing liquid composition applied to a method for forming a buried metal wiring on a semiconductor substrate.
[0002]
[Prior art]
In forming a metal wiring layer in a manufacturing process of a semiconductor device, a wiring-shaped groove is formed on the surface of the insulating film on the semiconductor substrate, a metal film made of copper or the like is deposited on the insulating film having the groove, and the metal film is A metal polishing process (Metal Chemical Mechanical Polishing, hereinafter referred to as “metal CMP”) is employed in wiring formation in which a metal layer remains only in the groove by a polishing process using a polishing apparatus and a polishing liquid.
[0003]
However, in this metal CMP, a recess called dishing occurs in the metal wiring layer remaining in the trench of the insulating film, and the cross-sectional area of the metal wiring layer is reduced, resulting in an increase in electrical resistance. There is. This dishing is said to occur when the surface of the metal wiring layer is polished or etched more excessively than the insulator surface by the polishing composition. In particular, copper, which is one of the main wiring metals, has a drawback in that dishing tends to occur because it is excessively etched by the polishing composition.
[0004]
Accordingly, a polishing liquid that does not have defects such as dishing in the metal layer is desired at the time of wiring formation while the etching action for polishing the metal film on the insulating film remains.
[0005]
As a conventional polishing liquid, JP-A-8-22970 discloses a high molecular weight organic compound having a molecular weight of 100 or more having at least one hydrophilic group comprising a carboxyl group or a salt thereof, a sulfone group or a salt thereof in the polishing liquid composition. Although the contained polishing liquid is described, there is no description regarding a specific acrylic polymer. Furthermore, it does not indicate that an acrylic acid polymer and an organic acid are used in combination, and when the metal layer is polished in metal CMP, the polishing rate is insufficient.
[0006]
Japanese Patent Laid-Open No. 10-168431 discloses a polishing liquid containing polyacrylic acid and polymethacrylic acid as a method for flattening the surface on a semiconductor wafer, but does not contain an organic acid and is a metal. When polishing a metal layer in CMP, the polishing rate is insufficient.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a polishing liquid composition that improves the polishing rate of a metal film on the surface to be polished having an insulating layer and a metal layer, and is excellent in preventing effects such as dishing of the metal wiring layer. .
[0008]
[Means for Solving the Problems]
The gist of the present invention is as follows.
[1] A polishing composition for polishing a surface to be polished having an insulating layer and a copper or copper alloy embedded metal wiring layer on a semiconductor substrate , comprising 0.1 to 30% by weight of an acrylic acid polymer, an organic acid A polishing composition containing 0.2 to 10% by weight, an abrasive and water and having a pH of 7 or less (hereinafter also referred to as a first polishing composition),
[2] Further, the polishing composition according to [1] containing an oxidizing agent (hereinafter also referred to as the second polishing composition) and [3] the molecular weight of the acrylic acid polymer is 500 to 50,000. It relates to the polishing composition according to [1] or [2].
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The acrylic acid polymer used in the present invention is represented by the formula (1):
[0010]
[Chemical 1]
[0011]
(Wherein R represents a hydrogen atom, a methyl group or an ethyl group, X represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group or an organic ammonium group, and the n Xs may be the same or different. Often, n represents the number of monomer repeats).
[0012]
In the formula (1), X is preferably a hydrogen atom, an ammonium group, an organic ammonium group such as monoethanolammonium, diethanolammonium, triethanolammonium and triethylammonium.
[0013]
The present invention has one major feature in using the acrylic acid-based polymer. By using a polishing liquid composition containing such an acrylic acid-based polymer, not only the polishing rate is improved, but also a metal film. Therefore, it is possible to prevent excessive etching, and to obtain an excellent effect that a polished surface free from defects such as dishing can be obtained.
[0014]
The acrylic acid polymer is, for example, an acrylic monomer such as acrylic acid, methacrylic acid, α-ethylacrylic acid, their alkali metal salts, ammonium salts, basic salts such as amine salts, and the like in an aqueous medium. Polymerization of 2,2'-azobisisobutylnitrile, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, ammonium persulfate, hydrogen peroxide, etc. It can be obtained by polymerization by a known polymerization method such as bulk polymerization or solution polymerization in the presence of an agent.
[0015]
The molecular weight of the acrylic acid-based polymer of the present invention is preferably from 500 to 50,000, particularly preferably from 500 to 10,000, more preferably from 500 to 5000, and most preferably from the viewpoint of improving the polishing rate and suppressing dishing. ˜3000 (converted to sodium polystyrene sulfonate by gel permeation chromatography (GPC)).
[0016]
The blending amount of the acrylic acid polymer in the first polishing composition is preferably 0.01 to 30% by weight, and 0.05 to 5% from the viewpoint of increasing the polishing rate and decreasing the etching rate to prevent dishing. % Is more preferable, and 0.1 to 3% by weight is more preferable.
[0017]
The organic acid used in the present invention is a compound having an acidic functional group. The functional group showing acidity includes carboxyl group, phosphone group, sulfone group, sulfine group, phenol group, enol group, thiophenol group, imide group, oxime group, aromatic sulfoamide group, primary and secondary nitro group Etc.
[0018]
Examples of the organic acid having a carboxyl group include monocarboxylic acid, dicarboxylic acid, hydroxycarboxylic acid, aminocarboxylic acid and the like. Specific examples of monocarboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, and valeric acid. , Caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pyruvic acid, etc .; dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, etc .; Examples of the hydroxycarboxylic acid include gluconic acid, tartaric acid, glycolic acid, lactic acid, citric acid, and malic acid; examples of the aminocarboxylic acid include ethylenediaminetetraacetic acid and nitrilotriacetic acid. Examples of the organic acid having a phosphonic group include 1-hydroxyethylidene-1,1-diphosphonic acid, and examples of the organic acid having a sulfone group include methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid; Examples of the organic acid having a sulfinic group include benzenesulfinic acid and p-toluenesulfinic acid. Among these, monocarboxylic acid, dicarboxylic acid, hydroxycarboxylic acid and aminocarboxylic acid are preferable, and acetic acid, oxalic acid, succinic acid, glycolic acid, lactic acid, citric acid, malic acid, tartaric acid, gluconic acid, ethylenediaminetetraacetic acid, nitrilotriline. More preferred is acetic acid. Moreover, you may use these organic acids individually or in mixture of 2 or more types. The molecular weight of these organic acids is preferably less than 500.
[0019]
In the present invention, by using such an organic acid, a complex is formed or bonded to various metals constituting the metal layer, particularly copper, and the metal layer is made a brittle layer, so that the metal layer can be easily removed during polishing. The effect of making is expressed. In particular, when an organic acid and an acrylic acid polymer are used in combination, a higher polishing rate can be realized and dishing can be prevented.
[0020]
The blending amount of the organic acid in the first polishing liquid composition is preferably 0.1 to 10 in order to secure a polishing rate at a practical level for removing the metal layer and prevent excessive etching of the metal layer. % By weight, more preferably 0.2 to 8% by weight, still more preferably 0.3 to 5% by weight.
[0021]
The water used in the present invention is used as a medium. The blending amount is preferably 60 to 99.8% by weight, more preferably 70 to 99.4% by weight, and still more preferably 80 to 99.0% by weight, from the viewpoint of efficiently polishing the workpiece.
[0022]
The pH of the polishing composition of the present invention is 7 or less from the viewpoint of keeping the polishing rate at a practical level and preventing dishing and removing fine scratches (scratches) on the surface. Preferably, 2-6 are more preferable, and 3-5 are more preferable. In order to adjust the pH within the above range, an inorganic acid such as nitric acid or sulfuric acid, an organic acid, a basic substance such as potassium hydroxide, sodium hydroxide, ammonia, or an amine can be appropriately blended as necessary. .
[0023]
The second polishing liquid composition of the present invention is obtained by further blending an oxidizing agent with the first polishing liquid composition. The oxidizing agent used in the present invention oxidizes a metal. In this invention, it is thought that the effect of oxidizing a metal layer and promoting the mechanical polishing effect of a metal layer is expressed by using such an oxidizing agent.
[0024]
Examples of the oxidizing agent include peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, nitric acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof, metal salts, sulfuric acid, and the like.
[0025]
Specific examples thereof include hydrogen peroxide, sodium peroxide, barium peroxide and the like as peroxides; potassium permanganate as permanganic acid or a salt thereof; and metal chromate as chromic acid or a salt thereof. Salt, dichromate metal salt, etc .; as nitric acid or its salt, iron nitrate (III), ammonium nitrate, etc .; Peroxosulfuric acid, sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, etc .; oxygen acids or their salts include hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, bromic acid , Iodic acid, perchloric acid, sodium hypochlorite, calcium hypochlorite, etc .; metal salts include iron (III) chloride, iron (III) sulfate, citric acid (III), ammonium iron (III), and the like. Preferable oxidizing agents include hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) ammonium sulfate, and hydrogen peroxide is particularly preferable. These oxidizing agents may be used alone or in admixture of two or more.
[0026]
The oxidizing agent is used in a state where water is used as a medium in the second polishing composition. The blending amount of the oxidizing agent in the second polishing liquid composition is preferably 0.1 to 60% by weight, more preferably 0.2% from the viewpoint of obtaining a practical level of polishing rate by rapid oxidation of the metal layer. -50% by weight, more preferably 0.3-30% by weight.
[0027]
The blending amount of the acrylic acid polymer in the second polishing composition is preferably 0.01 to 30% by weight, more preferably 0.05 to 5% by weight, and still more preferably 0.1 to 3% by weight. It is. The amount of water is preferably 10 to 99.7% by weight, more preferably 40 to 99% by weight, and still more preferably 60 to 98% by weight. The compounding amount of the organic acid is preferably 0.1 to 10% by weight, more preferably 0.2 to 8% by weight, and still more preferably 0.3 to 5% by weight.
[0028]
The 1st and 2nd polishing liquid composition of this invention which has the above structures is effective in the grinding | polishing system using a fixed grindstone. For example, by using the first or second polishing liquid composition during polishing using a fixed grindstone, not only the polishing rate can be improved, but also dishing of the metal layer can be prevented.
[0029]
Ken Migakueki compositions of the present invention has further contain a research Migakuzai, is used for a polishing method using free abrasive.
[0030]
As the abrasive, abrasive grains generally used for polishing can be used. For example, silicon dioxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride, manganese dioxide, silicon carbide, zinc oxide, Examples include diamond and magnesium oxide.
[0031]
Specific examples thereof include colloidal silica particles, fumed silica particles, and surface-modified silica particles as silicon dioxide; α-alumina particles, γ-alumina particles, δ-alumina particles, and θ-alumina particles as aluminum oxide. , Η-alumina particles, amorphous alumina particles, fumed alumina, colloidal alumina, etc. with different production methods, etc .; As cerium oxide, trivalent or tetravalent oxidation number, hexagonal crystal system, equiaxed Crystalline or face-centered cubic system, etc .; as zirconium oxide, the crystal system is monoclinic, tetragonal or amorphous, and other fumed zirconium with different production methods; , Titanium monoxide, Titanium trioxide, Titanium dioxide, and other fumed titania with different production methods, etc .; Silicon, β-silicon nitride, amorphous silicon nitride, other different forms, etc .; as manganese dioxide, α-manganese dioxide, β-manganese dioxide, γ-manganese dioxide, δ-manganese dioxide, ε-manganese dioxide, η -Manganese dioxide and the like. These abrasives may be used alone or in admixture of two or more.
[0032]
The average particle size of the primary particles of the abrasive is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, and particularly preferably 50 nm or more from the viewpoint of maintaining a constant polishing rate. Further, from the viewpoint of preventing scratches on the surface of the object to be polished, the thickness is preferably 1000 nm or less, more preferably 500 nm or less, still more preferably 300 nm or less, particularly preferably 200 nm or less, and most preferably 100 nm or less.
[0033]
In particular, when silicon dioxide is used as the abrasive, the average particle size of the primary particles is 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more from the viewpoint of improving the polishing rate.
[0034]
The average particle diameter of the primary particles of the abrasive is transmitted through 100 g of 0.1% polystyrene sodium sulfonate aqueous solution, 0.1 g of the abrasive, and then dispersing the abrasive to which ultrasonic waves are applied. It can be obtained by image analysis by observation with a scanning electron microscope.
[0035]
When the polishing composition of the present invention is used for forming a wiring of a semiconductor device, the polishing material used particularly preferably has a purity of preferably 98% by weight from the viewpoint of improving the synergistic effect with the acrylic acid polymer. % Or more, more preferably 99% by weight or more, particularly preferably 99.9% by weight or more of silica particles. As such an abrasive, fumed silica produced by high-temperature hydrolysis of a volatile silicon compound such as silicon tetrachloride in an acid hydrogen bath, or a method using an alkali silicate or ethyl silicate as a starting material. Colloidal silica is mentioned.
[0036]
The purity of the abrasive is determined as follows. That is, it can be measured by dissolving 1 to 3 g of an abrasive in an acid or alkaline aqueous solution and quantifying silicon ions by an ICP (plasma emission analysis) method.
[0037]
Such an abrasive is used in a so-called slurry state using water as a medium in the polishing composition of the present invention . The amount of the polishing composition of the present invention the abrasive can be variously selected according to the required quality and the like of the viscosity and the object to be polished of the polishing composition of the present invention, the polishing liquid excluding the abrasive It is 0.01-30 weight part with respect to 100 weight part of compositions, More preferably, it is 0.02-20 weight part, More preferably, it is 0.05-10 weight part.
[0038]
The polishing composition of the present invention is used for metal CMP, with the surface having an insulating layer and a metal layer as the object of polishing. Examples of the metal forming the metal layer include copper or a copper alloy, aluminum or an aluminum alloy, and tungsten. Among these, copper or a copper alloy is preferable particularly when used in the step of forming a buried metal wiring on a semiconductor substrate. When the polishing composition of the present invention is used for forming such a copper or copper alloy metal wiring layer, the effect of improving the polishing rate and the effect of suppressing dishing of the embedded metal wiring layer are particularly remarkably exhibited. Examples of the material for forming the insulating layer include silicon dioxide, nitride (eg, tantalum nitride, titanium nitride, etc.), fluorine-added silicon dioxide, Teflon, polyimide, organic SOG (spin on glass), hydrogen-containing SOG, and the like. .
[0039]
The shape of these objects to be polished is preferably a shape in which a wiring-shaped groove is formed on the surface of the insulating film on the semiconductor substrate and a metal is deposited on the insulating film including the groove. A barrier film made of tantalum, titanium, or a nitride thereof may be provided between the insulating film and the metal layer. In particular, when the metal layer is copper or a copper alloy, it is preferable to provide the barrier film because copper diffusion to the insulating layer can be prevented.
[0040]
【Example】
Examples 1-7 and Comparative Examples 1-4
Acrylic polymer are shown in Table 1 and an organic acid, respectively mixed with 31% hydrogen peroxide 2 wt% and the balance water in a content shown in Table 1, to obtain a set Narubutsu stirred. The obtained set Narubutsu 100 parts by weight, the abrasive 5 parts by weight shown in Table 1 was added, again mixing, after stirring, adjust pH, to obtain a polishing composition of the present invention. Each abrasive used was fumed silica (primary particle size: 50 nm) and colloidal silica (primary particle size: 30 nm). In addition, the object to be polished was polished by a single-side polishing machine under the following conditions.
[0041]
<Setting conditions of single-sided machine>
Single-sided machine used: Engis single-sided machine (plate size 30cm)
Processing pressure: 300gf / cm ²
Polishing pad: Upper layer: IC1000 (Rodel Nitta), Lower layer: SUBA400 (Rodel Nitta)
Plate rotation speed: 60rpm
Polishing liquid composition supply flow rate: 100mL / min
Polishing time: 2 minutes [0042]
Moreover, the characteristics of the polishing composition such as the relative polishing rate and dishing of the surface to be polished were evaluated according to the following methods.
[0043]
[Relative polishing speed]
The object to be polished used for obtaining the relative polishing rate is a silicon substrate in which a copper film is formed on the silicon substrate by electroplating or the like. The polishing rate was determined by measuring 20 changes in the copper film before and after polishing and dividing it by the polishing time, and the relative value was determined based on Comparative Example 1 or 2. The results are shown in Table 1.
[0044]
[Dishing]
For dishing evaluation, five 20 mm square chips were cut out from a wafer with copper damascene wiring pattern (SKW6-2, “SKW6-2”, size: 200 mm), fixed to a ceramic adhesive plate, and then subjected to the above conditions. The sample was polished and used as a dishing evaluation sample. The dishing evaluation was performed by observation with a scanning electron microscope of a cross section of a pattern having a wiring width size of 1500 μm × 1500 μm. The results are shown in Table 1. In the table, “No” indicates that there is no dishing, and “Yes” indicates that there is one or more dishes.
[0045]
[Table 1]
[0046]
From the results of Examples, it can be seen that by using an acrylic acid polymer and an organic acid in combination, a sufficient polishing rate can be exhibited and dishing can be prevented. Further, by polishing at pH 7 or less, a sufficient polishing rate can be obtained.
[0047]
【The invention's effect】
By using the polishing composition of the present invention for polishing a surface to be polished having an insulating layer and a metal layer, the effect of improving the polishing rate of the metal film and preventing the occurrence of defects such as dishing in the wiring metal layer is achieved. The

Claims (2)

A polishing liquid composition for polishing a surface to be polished having an insulating layer and a copper or copper alloy embedded metal wiring layer on a semiconductor substrate, the following formula:
(Wherein R represents a hydrogen atom, a methyl group or an ethyl group, X represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group or an organic ammonium group, and the n Xs may be the same or different. Well, n represents the number of repeating monomers)
0.1 to 3 % by weight of an acrylic acid polymer having a molecular weight of 500 to 3000, 0.2 to 10% by weight of an organic acid, silicon dioxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride A polishing composition comprising a polishing material selected from the group consisting of manganese dioxide, silicon carbide, zinc oxide, diamond and magnesium oxide , and water , and having a pH of 7 or less.   The polishing composition according to claim 1, further comprising an oxidizing agent.